TWI883421B - Projection substrate and eyeglass type terminal - Google Patents

Abstract

A projection substrate is used to transmit at least a portion of light incident from a first surface to a second surface on the opposite side of the first surface, and to project image light onto the second surface. The projection substrate comprises: an incident area for the projection light to be incident; a branch area having a first diffraction grating for guiding the projection light incident from the incident area; and an output area having a second diffraction grating for guiding a portion of the projection light incident from the branch area and then emitting a portion of the projection light from the second surface. The incident area guides the projection light to the branch area. The branch region diverts a portion of the projection light toward the exit region, the first diffraction grating has a plurality of first convex-concave portions formed by first convex portions and first concave portions repeatedly formed in a first direction for guiding the projection light, and a first filling factor, a ratio of a width of the first convex portion in the first direction to a first period of the first convex-concave portion in one of the plurality of first divided regions, is far from 0.5 compared with the first filling factor of a first divided region closer to the incident region than the first divided region.

Description

Projection substrate and eyeglass type terminal

The present invention relates to a projection substrate and a glasses-type terminal.

Conventionally, there are known eyeglass-type devices, head-mounted displays, and the like that use an optical system including a waveguide to display a two-dimensional image for a user to view (see, for example, Japanese Patent Application Publication No. 2017-207686).

[Problems that the invention aims to solve] In such devices, the optical system needs to be installed in a limited space, so the optical system sometimes becomes complicated. In addition, if a simple optical system is used, the brightness of the image projected onto the display area may be uneven.

Therefore, the present invention is completed in view of these aspects, and its purpose is to reduce the uneven brightness of the projected image viewed by the user with a simple structure. [Means for solving the problem]

In a first form of the present invention, a projection substrate is provided, which is used to transmit at least a portion of light incident from a first surface to a second surface on the opposite side of the first surface, and to project image light onto the second surface. The projection substrate includes: an incident area for incident projection light for projecting the image light; a branch area having a first diffraction grating for guiding the projection light incident from the incident area; and an exit area having a second diffraction grating for guiding a portion of the projection light incident from the branch area and then emitting a portion of the projection light from the second surface. The incident area guides the incident projection light to the branch area. The branch area diverts a portion of the projection light toward the exit area, the first diversion grating has a plurality of first convex-concave portions consisting of a first convex portion and a first concave portion, the plurality of first convex-concave portions are formed in a repetitive manner in a first direction for guiding the projection light, the branch area has a plurality of first segmented areas, a first filling factor, which is a ratio of a width of the first convex portion in the first direction to a first period of the first convex-concave portion in a first segmented area, is within a range not including a specified value, and a first filling factor of a first segmented area that is closer to the incident area than the first segmented area is within a range including the specified value.

Alternatively, the first periods of the first concave-convex portions of each of the plurality of first divided regions may be the same.

It may also be that the depth of the first concave-convex portion of the one first division area is greater than the depth of the first concave-convex portion of the first division area closer to the incident area than the one first division area, and the greater the absolute value of the difference between the depth of the first concave-convex portion of the one first division area and the depth of the first concave-convex portion of the first division area closer to the incident area than the one first division area is, the smaller the absolute value of the difference between the first filling factor of the one first division area and the first filling factor of the first division area closer to the incident area than the one first division area is.

Alternatively, the specified value is 0.5, the first filling factor of the first segmented area among the multiple first segmented areas that is farthest from the incident area is in the range of less than 0.35 or greater than 0.65, and the first filling factor of the first segmented area that is closer to the incident area than the first segmented area is in the range of greater than 0.3 and less than 0.7.

Alternatively, the second diffraction grating has a plurality of second convex-concave portions consisting of second convex portions and second concave portions, the plurality of second convex-concave portions are formed in a repetitive manner in a second direction for guiding the projection light, the exit region has a plurality of second divided regions, and in a second divided region among the plurality of second divided regions which is closer to the branch region than a second divided region, a ratio of the width of the second convex portion in the second direction to the second period of the second convex-concave portion, that is, a second filling factor, is within a range including the specified value.

Alternatively, the second periods of the second concave-convex portions of each of the plurality of second divided regions may be the same.

It may also be that the depth of the second concave-convex portion of the one second dividing area is greater than the depth of the second concave-convex portion of the second dividing area closer to the branch area than the one second dividing area. The greater the absolute value of the difference between the depth of the second concave-convex portion of the one second dividing area and the depth of the second concave-convex portion of the second dividing area closer to the branch area than the one second dividing area, the smaller the absolute value of the difference between the width of the second convex portion in the one second dividing area in the second direction relative to the second period of the second concave-convex portion, that is, the second filling factor and the second filling factor of the second dividing area closer to the branch area than the one second dividing area.

Alternatively, the prescribed value is 0.5, the second filling factor of the one second partition area is within a range not including the prescribed value, and the second filling factor of the second partition area closer to the branch area than the one second partition area is within a range including the prescribed value.

It may also be that, ideally, the prescribed value is 0.5, the first period of each of the plurality of first divided regions is greater than 50 nm and less than 1 μm, the depth of the first concave-convex portion of the one first divided region is greater than 50 nm and less than 800 nm, the first filling factor of the one first divided region is less than 0.35 or greater than 0.65, the depth of the first concave-convex portion of the first divided region closer to the incident region than the one first divided region is greater than 5 nm and less than 100 nm, the first filling factor of the first divided region closer to the incident region than the one first divided region is greater than 0.3 and less than 0.7, the second period of each of the plurality of second divided regions is greater than 100 nm and less than 1 μm, the depth of the second concave-convex portion of the one second divided region is greater than 50 nm and less than 800 nm nm or less, the second filling factor of the second segmentation region is less than 0.35 or greater than 0.65, the depth of the second concave-convex portion of the second segmentation region closer to the branch region than the second segmentation region is greater than 5 nm and less than 100 nm, and the second filling factor of the second segmentation region closer to the branch region than the second segmentation region is greater than 0.3 and less than 0.7.

In a second form of the present invention, a spectacle-type terminal is provided for a user to wear, and the spectacle-type terminal comprises: the projection substrate described in the first form, which is provided as at least one of the lens for the right eye and the lens for the left eye of the user, so that at least a part of the light incident from the first surface is transmitted to the eye of the user, and the image light is projected onto the second surface; a frame, which fixes the projection substrate; and a projection unit, which is provided on the frame, and irradiates the projection light used to project the image light onto the emission area onto the incident area of the projection substrate. [Effect of the invention]

According to the present invention, the following effect is achieved: the uneven brightness of the projection image viewed by the user can be reduced with a simple structure.

<Structural example of the eyeglass type terminal 10> FIG. 1 shows a structural example of the eyeglass type terminal 10 of the present embodiment. In the present embodiment, three axes orthogonal to each other are set as the X axis, the Y axis, and the Z axis. The eyeglass type terminal 10 is a wearable device worn by a user, for example. The eyeglass type terminal 10 allows the user to view the scenery through the eyeglasses and projects image light onto a display area provided on the projection substrate 100. The eyeglass type terminal 10 includes a projection substrate 100, a frame 110, and a projection unit 120.

The projection substrate 100 transmits at least a portion of light incident from the first surface to the user's eyes, and projects the image light onto the second surface. Here, the first surface of the projection substrate 100 is the surface facing the opposite side of the user when the user wears the eyeglass-type terminal 10. Moreover, the second surface of the projection substrate 100 is the surface facing the user when the user wears the eyeglass-type terminal 10. FIG. 1 shows an example in which the first surface and the second surface of the projection substrate 100 are arranged substantially parallel to the XY plane. The projection substrate 100 is, for example, a substrate in which a diffraction grating functioning as a waveguide is formed on a glass substrate. The projection substrate 100 will be described later.

The frame 110 fixes the projection substrate 100. The frame 110 is provided with the projection substrate 100 as at least one of the lens for the right eye and the lens for the left eye of the user. FIG. 1 shows an example in which the frame 110 is provided with the projection substrate 100a as the lens for the right eye of the user, and the projection substrate 100b as the lens for the left eye.

The frame 110 may also be replaced with a projection substrate 100 to serve as a lens for the right eye or the left eye of the user. In addition, the frame 110 may also be provided with a projection substrate 100 to serve as a lens for both eyes of the user. In this case, the frame 110 may also have the shape of goggles. The frame 110 has a temple, a strap, and other parts so that the user can wear the eyeglass-type terminal 10.

The projection unit 120 is provided on the frame 110, and irradiates projection light for projecting image light onto the projection substrate 100 toward the projection substrate 100. The frame 110 is provided with one or more such projection units 120. FIG. 1 shows an example in which the frame 110 is provided with a projection unit 120a for irradiating the projection light L1 onto the projection substrate 100a, and a projection unit 120b for irradiating the projection light L2 onto the projection substrate 100b.

The projection unit 120 may be provided at a portion of the frame 110 where the projection substrate 100 is fixed, or at a side support of the frame 110. Ideally, the projection unit 120 is provided in a manner that is integrated with the frame 110. The projection unit 120, for example, irradiates the projection substrate 100 with projection light having one wavelength so that the user can view a monochrome image. Furthermore, the projection unit 120 may irradiate the projection substrate 100 with projection light having multiple wavelengths so that the user can view an image having multiple colors.

FIG. 2 schematically shows the optical path of the projection light in the eyeglass-type terminal 10 of the present embodiment. The projection unit 120 irradiates the projection light to the incident area 210 provided on the projection substrate 100. The incident area 210 guides the projection light into the substrate of the projection substrate 100. The projection substrate 100 then emits the projection light guided in the substrate from the emission area 230 as image light. The incident area 210 and the emission area 230 will be described later.

FIG3 schematically shows the optical path of the projection light in the projection substrate 100 of the present embodiment. Although it will be described later, the projection substrate 100 has an incident area 210, a branch area 220, and an output area 230. The projection light L is incident on the incident area 210, and is output from the output area 230 as image light P via the branch area 220. As the projection light L moves away from the incident area 210, the branch area 220 guides the projection light L to the output area 230 in parts.

Similarly, the emission region 230 also emits a portion of the projection light L as a portion of the image light P as the projection light L moves away from the branch region 220 . Thus, the projection substrate 100 emits the projection light L incident on the incident region 210 as the image light P from the emission region 230 .

Here, the following example is considered: the branch region 220 guides the projection light L to the exit region 230 at a certain ratio in the entire region of the branch region 220. At this time, as the projection light L moves away from the incident region 210, the light amount of the projection light L decreases, so the projection light L incident from the branch region 220 to the exit region 230 may have different intensities depending on the distance from the incident region 210.

Similarly, consider an example in which the exit area 230 emits the projection light L as the image light P at a certain ratio in the entire area of the exit area 230. At this time, as the projection light L moves away from the branch area 220, the light amount of the projection light L decreases, so the image light P emitted from the exit area 230 may have different intensities depending on the distance from the incident area 210 and the distance from the exit area 230. For example, the brightness of the upper left pixel of the image projected from the exit area 230 may gradually decrease toward the lower right pixel. The projection substrate 100 of the present embodiment reduces such uneven brightness.

<An example of projection light and image light> FIG. 4 shows an example of projection light L irradiated to the projection substrate 100 by the projection unit 120 of the present embodiment and image light P emitted by the projection substrate 100. The projection unit 120 irradiates the projection light L toward the second surface of the projection substrate 100 located in the +Z direction, for example. The projection light L corresponds to the image seen by the user. For example, when a screen is provided on a surface substantially parallel to the XY plane to project the projection light L, an image M1 for the user to view is displayed on the screen. The image seen by the user is, for example, an augmented reality (AR) image or a virtual reality (VR) image produced by a processor of the projection unit 120. In this way, the projection unit 120 irradiates a plurality of light rays forming the image M1 on a surface substantially parallel to the XY plane as projection light L.

In the present embodiment, the following example is described, that is, the projection unit 120 projects a substantially rectangular image M1 with the X-axis direction as the long side direction onto a surface substantially parallel to the XY plane. Moreover, in FIG4 , five of the multiple light rays irradiated by the projection unit 120 are represented as input light rays 20. For example, the light corresponding to the upper left pixel of the image is set as the first input light 20a, the light corresponding to the lower left pixel of the image is set as the second input light 20b, the light corresponding to the central pixel of the image is set as the third input light 20c, the light corresponding to the upper right pixel of the image is set as the fourth input light 20d, and the light corresponding to the lower right pixel of the image is set as the fifth input light 20e.

The projection unit 120 irradiates the incident area 210 of the projection substrate 100 with such projection light L, for example, to form an upright virtual image at infinity or at a predetermined position. The projection light incident on the incident area 210 is emitted from the emission area 230 through the branch area 220 as image light P. The image light P is emitted from the emission area 230 and is incident on the user's eye separated by a distance d from the projection substrate 100. In addition, the image light P is imaged as an image M2 on the retina of the user's eye. In this way, the image light P includes a plurality of light beams imaged as the image M2.

In Fig. 4, five of the plurality of light beams irradiated from the circular area C of the emission area 230 of the projection substrate 100 and imaged at a predetermined position are represented as output light beams 30. For example, the light beam imaged as the lower right pixel of the image is set as the first output light beam 30a, the light beam imaged as the upper right pixel of the image is set as the second output light beam 30b, the light beam imaged as the central pixel of the image is set as the third output light beam 30c, the light beam imaged as the lower left pixel of the image is set as the fourth output light beam 30d, and the light beam imaged as the upper left pixel of the image is set as the fifth output light beam 30e.

Each light beam corresponds to a plurality of input light beams 20 incident from the projection unit 120. For example, the first output light beam 30a corresponds to the first input light beam 20a, and the first input light beam 20a includes a plurality of light beams generated by multiple branches and multiple diffractions between the incident area 210 and the exit area 230 of the projection substrate 100. Similarly, the second output light beam 30b corresponds to the second input light beam 20b, the third output light beam 30c corresponds to the third input light beam 20c, the fourth output light beam 30d corresponds to the fourth input light beam 20d, and the fifth output light beam 30e corresponds to the fifth input light beam 20e.

In other words, the image M2 formed on the retina of the user's eye by the image light P emitted from the emission area 230 corresponds to the image M1 projected by the projection light L irradiated by the projection unit 120. Thus, the user wearing the eyeglass type terminal 10 can feel that the image M2 is superimposed on the scenery seen through the projection substrate 100 and projected on the second surface of the projection substrate 100. In other words, the emission area 230 functions as a display area for displaying the image M2 corresponding to the image M1 projected by the projection light L.

FIG4 shows an example in which the image M2 observed by the user is an image in which the image M1 projected by the projection light L is reversed up and down and left and right. Furthermore, the image M1 projected by the projection light L may be a static image or a dynamic image instead. Next, the projection substrate 100 that emits the image light P corresponding to the incident projection light L as described above will be described.

<Structural example of projection substrate 100> FIG. 5 shows a structural example of the projection substrate 100 of the present embodiment. FIG. 5 shows an example in which the first surface and the second surface of the projection substrate 100 are arranged substantially parallel to the XY plane. The projection substrate 100 is a substrate for transmitting at least a portion of light incident from the first surface to the second surface on the opposite side of the first surface, and for projecting image light onto the second surface. As an example, the projection substrate 100 is a glass substrate. The projection substrate 100 includes an incident region 210, a branch region 220, and an exit region 230.

<Example of the incident area 210> The incident area 210 is used for incident projection light for image light projection, and guides the incident projection light toward the branch area 220. FIG. 5 shows an example in which the incident area 210 has a circular shape on a surface substantially parallel to the XY plane, but the invention is not limited thereto. The incident area 210 may have an elliptical, polygonal, trapezoidal, or other shape as long as it can guide the projection light to the branch area 220.

The incident area 210 has a diversion grating having a plurality of first grooves 212 formed in an input pupil expander (IPE) cycle. In other words, the plurality of first grooves 212 are arranged on the upper surface of the projection substrate 100 in the same direction with a predetermined groove width and interval, thereby functioning as a diversion grating. The incident area 210 has a reflective or transmissive diversion grating, and guides the projection light toward the direction of the branch area 220 by reflective diffraction or transmissive diffraction.

The IPE period of the plurality of first grooves 212 is, for example, in the range of about 10 nm to about 10 μm. The IPE period is preferably in the range of about 100 nm to about 1 μm. The IPE period is more preferably in the range of about 200 nm to about 800 nm. The depth of the plurality of first grooves 212 is in the range of about 1 nm to about 10 μm. The depth of the plurality of first grooves 212 is preferably in the range of about 50 nm to about 800 nm.

The filling factor of the plurality of first grooves 212 is in the range of about 0.05 to about 0.95. The filling factor of the plurality of first grooves 212 is preferably in the range of about 0.3 to about 0.7. Here, the filling factor is a value obtained by dividing the distance between two adjacent first grooves 212 by the IPE period. Furthermore, sometimes the distance between two adjacent first grooves 212 is referred to as a line, the width of the first groove 212 is referred to as a space, and the IPE period is referred to as a pitch. In this case, the pitch is the sum of the line and the space, and the filling factor is a value obtained by dividing the line by the pitch.

The plurality of first grooves 212 are arranged, for example, in a direction from the incident region 210 toward the branch region 220. Here, the traveling direction of the projection light from the incident region 210 toward the branch region 220 is set as the first direction. FIG. 5 shows an example in which the first direction is a direction substantially parallel to the X-axis direction, and the first grooves 212 extending in a direction substantially parallel to the Y-axis direction are arranged along the first direction. The projection light is converged and incident on the incident region 210, so the incident region 210 guides the projection light to the branch region 220 in a manner having a spread angle with the first direction as the center within the plane of the projection substrate 100.

<Example of branch region 220> The branch region 220 guides a portion of the projection light incident from the incident region 210 toward the exit region 230. The branch region 220 is a region provided on a surface substantially parallel to the XY plane where the projection light passes. The branch region 220 has a reflective diffraction grating, and guides the projection light in the direction of the exit region 230 by reflective diffraction. The branch region 220 has, for example, a rectangular shape with the first direction being the long side direction.

Furthermore, since the projection light travels while expanding with the first direction as the center, the branch region 220 preferably has a shape that expands in the following manner, that is, as it moves away from the incident region 210, it passes through the incident region 210 and moves away from the first direction, which is the direction in which the projection light travels. The branch region 220 has a shape such as a trapezoid or a fan on a surface that is substantially parallel to the XY plane. FIG. 5 shows an example in which the branch region 220 has a trapezoidal shape. The branch region 220 of this shape can be formed corresponding to the region in which the projection light travels while expanding on the XY plane, thereby efficiently guiding the projection light.

In the branch region 220, a plurality of first concave-convex portions consisting of a first convex portion and a first concave portion are repeatedly formed in a first direction. Hereinafter, the first concave-convex portion is referred to as a second groove portion 222. That is, the branch region 220 has a first diffraction grating having a plurality of second groove portions 222 formed in a first period. In other words, the plurality of second groove portions 222 are arranged in the same direction on the upper surface of the projection substrate 100 with a predetermined groove width and interval, thereby functioning as a diffraction grating. The branch region 220 functions as a reflective diffraction grating, for example, to guide the projection light to the exit region 230.

The first period of the plurality of second grooves 222 is a period different from the IPE period of the plurality of first grooves 212. Ideally, in order to guide the projection light to the exit area 230, an appropriate period is selected as the first period. The first period is, for example, in the range of about 10 nm to about 10 μm. The first period is preferably in the range of about 50 nm to about 1 μm. The first period is more preferably in the range of about 100 nm to about 700 nm. The depth of the plurality of second grooves 222 is in the range of about 1 nm to about 10 μm. The depth of the plurality of second grooves 222 is preferably in the range of about 5 nm to about 800 nm.

The plurality of second grooves 222 are arranged, for example, along a predetermined direction. For example, the direction from the branch region 220 toward the emission region 230 is set as the second direction, and the angle formed by the first direction and the second direction is set as the first angle. At this time, the plurality of second grooves 222 are formed along a direction that is inclined toward the second direction at an angle of 1/2 of the first angle relative to the first direction. FIG. 5 shows the following example, that is, the second direction is a direction substantially parallel to the Y-axis direction, the first angle is substantially 90 degrees, and the plurality of second grooves 222 are arranged along a direction that is inclined toward the second direction at a degree of substantially 45 relative to the first direction.

The branch region 220 has a plurality of first division regions 224 arranged along the traveling direction of the incident projection light. The depths of the second grooves 222 formed in the plurality of first division regions 224 are different. In other words, in the branch region 220, the second grooves 222 are formed in such a manner that the proportion of the light guided to the exit region 230 in the input projection light is different for each first division region 224.

It is desirable that the branch region 220 has three or more first division regions 224. The first periods of the plurality of second grooves 222 formed in each of the plurality of first division regions 224 are all the same, for example. In this way, the branch region 220 is divided into the plurality of first division regions 224, and the light amount of the projection light guided to the exit region 230 is made different for each first division region 224, so that the projection light having different intensities depending on the distance from the incident region 210 is guided to the exit region 230, and the light amount distribution in the direction perpendicular to the traveling direction of the projection light is adjusted to be substantially constant.

For example, the second groove 222 is formed in such a manner that the depth of the second groove 222 provided in one first segmentation region 224 is greater than the depth of the second groove 222 provided in a first segmentation region 224 closer to the incident region 210 than the first segmentation region 224. In this case, the farther from the incident region 210, the greater the variation rate of the depth of the second groove 222 of two adjacent first segmentation regions 224 among the plurality of first segmentation regions 224.

As an example, as shown in Fig. 5, consider the branch region 220 having three first division regions 224. Here, the first division region 224a closest to the incident region 210 among the three first division regions 224 is configured such that the second groove portion 222 is formed so as to guide approximately 1/4 of the incident projection light to the exit region 230. At this time, the remaining approximately 3/4 of the projection light incident on the first division region 224a closest to the incident region 210 is incident on the adjacent first division region 224b.

The first segmented area 224b which is the second closest to the incident area 210 is configured such that the depth of the second groove 222 is formed so as to guide light of approximately 1/3 of the incident projection light to the exit area 230. In other words, the depth of the second groove 222 of the first segmented area 224b which is the second closest to the incident area 210 is formed to be greater than the depth of the second groove 222 of the first segmented area 224a so as to guide light of 4/3 times the amount of light as compared with the first segmented area 224a which is the closest to the incident area 210 to the exit area 230. Such first segmented area 224b guides light of approximately 1/4 of the amount of projection light incident on the first segmented area 224a which is the closest to the incident area 210 to the exit area 230.

Furthermore, the remaining approximately 1/2 of the projection light incident on the first segmented area 224a closest to the incident area 210 is incident on the adjacent first segmented area 224c. The first segmented area 224c, which is the third closest to the incident area 210, is configured such that the depth of the second groove 222 is formed so as to guide approximately 1/2 of the incident projection light to the exit area 230. In other words, the depth of the second groove 222 of the first segmented area 224c, which is the third closest to the incident area 210, is formed to be greater than the depth of the second groove 222 of the first segmented area 224b so as to guide 3/2 times the light of the first segmented area 224b, which is the second closest to the incident area 210, to the exit area 230.

Furthermore, the variation rate of the depth of the second groove portion 222 of two adjacent first divided regions 224 among the three first divided regions 224 is formed to be larger as it is farther from the incident region 210. Furthermore, the first divided region 224c which is the third closest to the incident region 210 guides approximately 1/4 of the light amount of the projection light incident on the first divided region 224a which is closest to the incident region 210 to the exit region 230. As can be seen from the above example, the branch region 220 sets the light amount of the projection light guided to the exit region 230 to a predetermined value differently for each first divided region 224, thereby making it possible to set the light amount of the projection light guided to the exit region 230 corresponding to each first divided region 224 to a substantially fixed distribution and guide the projection light to the exit region 230. That is, the branch area 220 can adjust the light quantity distribution in the direction perpendicular to the traveling direction of the projection light incident from the incident area 210 to be substantially constant. Therefore, the eyeglass-type terminal 10 can reduce the uneven brightness of the projection image viewed by the user.

Furthermore, the branch region 220 may also have a first reflection region 226 as one of the first segment regions 224 at a position farthest from the incident region 210. FIG5 shows an example in which the branch region 220 has three first segment regions 224 and the first reflection region 226. The first reflection region 226 reflects at least a portion of the light that has passed through the plurality of first segment regions 224 again toward the plurality of first segment regions 224. The first reflection region 226 has a second groove portion 222 having a greater depth than the second groove portion 222 of the adjacent first segment region 224.

For example, it is desirable that the depth of the second groove 222 of the first reflection region 226 is approximately three times or more the maximum depth of the second grooves 222 of the plurality of first segmented regions 224. More preferably, the depth of the second groove 222 of the first reflection region 226 is approximately ten times or more the maximum depth of the second grooves 222 of the plurality of first segmented regions 224. Furthermore, the second grooves 222 of the first reflection region 226 may also be arranged along the first direction.

Since the branch region 220 has such a first reflection region 226, the plurality of first division regions 224 guide at least a portion of the light reflected by the first reflection region 226 to the output region 230. Thus, the branch region 220 can guide more projection light to the output region 230. Furthermore, the depth of the second groove portion 222 of the plurality of first division regions 224 can also be determined so that each first division region 224 includes the reflected light formed by the first reflection region 226 and the light amount of the projection light guided to the output region 230 is substantially constant.

The widths of the convex and concave portions of the plurality of first division regions 224 are formed so that the first filling factor becomes a predetermined value. The first filling factor is the ratio of the width of the first convex portion of one first division region 224 in the first direction to the first period of the second groove portion 222 .

FIG6 is a diagram for explaining the first filling factor. A plurality of second grooves 222 are formed on the glass substrate 112. Line 240 is the width of the first convex portion 222a of the second groove 222. Space 242 is the width of the first concave portion 222b of the second groove 222. Spacing 244 is the sum of line 240 and space 242, and is the length of the first period. The first filling factor is the value obtained by dividing line 240 by spacing 244. Furthermore, a length 248 from the first concave portion 222b to the glass substrate 112 is in the range of greater than 10 nm and less than 500 nm. The length 248 is preferably in the range of greater than 30 nm and less than 200 nm. Depth 246 is the depth of the second groove 222.

The first filling factor of the first reflection area 226, which is one of the first segmented areas 224, is within a range that does not include a specified value. The predetermined value is, for example, 0.5. To give a specific example, the first filling factor of the first reflection area 226 is within a range that does not include the specified value 0.5 and is less than 0.35 or greater than 0.65. The first filling factor of the first segmented area 224 that is closer to the incident area 210 than the first reflection area 226 is within a range that includes the specified value 0.5. To give a specific example, the first filling factors of the first segmented area 224a, the first segmented area 224b, and the first segmented area 224c are within a range that is greater than 0.3 and less than 0.7.

Regarding the difference between the first filling factor of the first reflection region 226 and the first segment region 224c closer to the incident region 210 than the first reflection region 226, the greater the absolute value of the difference between the depth of the second groove portion 222 of the first reflection region 226 and the depth of the second groove portion 222 of the first segment region 224c, the smaller it is. To give a specific example, when the difference between the depth of the second groove portion 222 of the first reflection region 226 and the depth of the second groove portion 222 of the first segment region 224c is 180 nm, the difference between the first filling factor of the first reflection region 226 and the first segment region 224c closer to the incident region 210 than the first reflection region 226 is 0.35. On the other hand, when the difference between the depth of the second groove 222 of the first reflection area 226 and the depth of the second groove 222 of the first segmentation area 224c is 680 nm, the difference between the first filling factor of the first reflection area 226 and the first segmentation area 224c closer to the incident area 210 than the first reflection area 226 is 0.30.

<Example of the emission area 230> The emission area 230 guides at least a portion of the projection light incident from the branch area 220 and emits it from the second surface of the projection substrate 100 as image light. FIG5 shows an example in which the emission area 230 has a rectangular shape with the X-axis direction as the long side direction on a surface substantially parallel to the XY plane, but is not limited thereto. The emission area 230 may have any shape as long as it can guide the projection light and emit it as image light, for example, it may have a rectangular shape, a square shape, a trapezoid shape, etc. with the Y-axis direction as the long side direction.

A plurality of third grooves 232 are formed in the emission area 230, and the plurality of third grooves 232 are a plurality of second concave-convex portions composed of second convex portions and second concave portions formed in a repeated manner in the second direction. That is, the emission area 230 has a second diffraction grating having a plurality of third grooves 232 formed in a second period. In other words, the plurality of third grooves 232 are arranged on the upper surface of the projection substrate 100 in the same direction with a predetermined groove width and interval, thereby functioning as a diffraction grating. The emission area 230 has a reflective or transmissive diffraction grating, and guides the image light toward the user's eyes by reflective diffraction or transmissive diffraction.

The second period of the plurality of third grooves 232 provided in the exit area 230 is a period different from the first period of the plurality of second grooves 222 in the branch area 220. The second period of the plurality of third grooves 232 in the exit area 230 may also be the same period as the IPE period of the plurality of first grooves 212 in the incident area 210. In this way, by making the periods of the diffraction grating provided in the incident area 210 where the projection light is incident and the exit area 230 where the image light is emitted consistent, the distortion of the image viewed by the user can be reduced.

The second period is formed, for example, in a range of about 10 nm to about 10 μm. The second period is preferably formed in a range of about 100 nm to about 1 μm. The second period is more preferably formed in a range of about 200 nm to about 800 nm. The depth of the plurality of third grooves 232 is formed in a range of about 1 nm to about 10 μm. The depth of the plurality of third grooves 232 is preferably formed in a range of about 5 nm to about 800 nm.

The plurality of third grooves 232 are arranged, for example, along the second direction from the branch region 220 toward the emission region 230. Fig. 5 shows an example in which the third grooves 232 extending along the first direction are arranged along the second direction.

The exit region 230 has a plurality of second divided regions 234 arranged along the traveling direction of the projection light incident from the branch region 220, similarly to the branch region 220. The depths of the third grooves 232 formed in the plurality of second divided regions 234 are different. In other words, in the exit region 230, the third grooves 232 are formed so that the proportion of light emitted as image light in the input projection light is different for each second divided region 234.

It is desirable that the emission region 230 has two or more second segment regions 234. For example, the depth of the third groove 232 provided in one second segment region 234 is formed to be greater than the depth of the third groove 232 provided in the second segment region 234 closer to the branch region 220 than the one second segment region 234. Moreover, in the case where the emission region 230 has three or more second segment regions 234, the variation rate of the depth of the third groove 232 of two adjacent second segment regions 234 may be greater as the distance from the branch region 220 increases. Furthermore, the second periods of the plurality of third grooves 232 are all the same, for example.

As described above, the emission area 230 is divided into a plurality of second divided areas 234, so that the light amount of light emitted as image light is different for each second divided area 234. Thus, the emission area 230 can guide the projection light as image light, similarly to the plurality of first divided areas 224 of the branch area 220, and when an observer observes the image light as an image, the light amount distribution of the entire image can be adjusted to be substantially constant.

The emission region 230 may further include a second reflection region 236 as one of the second segment regions 234 at a position farthest from the branch region 220. FIG5 shows an example in which the emission region 230 includes two second segment regions 234 and a second reflection region 236. The second reflection region 236 reflects at least a portion of light that has passed through the plurality of second segment regions 234 back toward the plurality of second segment regions 234. The second reflection region 236 includes a third groove portion 232 having a greater depth than the third groove portion 232 of the adjacent second segment region 234.

For example, it is desirable that the depth of the third groove 232 of the second reflection region 236 is approximately three times greater than the maximum depth of the third grooves 232 of the plurality of second segmented regions 234. More desirably, the depth of the third groove 232 of the second reflection region 236 is approximately ten times greater than the maximum depth of the third grooves 232 of the plurality of second segmented regions 234.

Since the emission region 230 has such a second reflection region 236, the plurality of second divided regions 234 emit at least a portion of the light reflected by the second reflection region 236 from the second surface of the projection substrate 100 as image light. Thus, the emission region 230 can emit more projection light as image light, similarly to the branch region 220. Furthermore, the depth of the third groove portion 232 of the plurality of second divided regions 234 can also be determined so that each second divided region 234 includes the reflected light formed by the second reflection region 236, and the light amount of the light emitted as image light is substantially constant.

The widths of the convex and concave portions of each of the plurality of second divided regions 234 are formed so that the second filling factor becomes a predetermined value. The second filling factor is the ratio of the width of the second convex portion in the second direction to the second period of the third groove portion 232 .

The second filling factors of the second partition area 234a, the second partition area 234b, and the second partition area 234c are within a range including a specified value. The specified value is, for example, 0.5. To give a specific example, the second filling factors of the second partition area 234a, the second partition area 234b, and the second partition area 234c are within a range of 0.3 or more and 0.7 or less including the specified value 0.5.

The second filling factor of the second reflection area 236 is within a range that does not include the specified value 0.5. For example, the second filling factor of the second reflection area 236 is less than 0.35 or greater than 0.65, but is not limited thereto.

Moreover, the greater the absolute value of the difference between the depth of the third groove portion 232 of the second reflection region 236 and the depth of the third groove portion 232 of the second segment region 234, the smaller the absolute value of the difference between the second filling factor of the second reflection region 236 and the second segment region 234. To give a specific example, when the difference between the depth of the third groove portion 232 of the second reflection region 236 and the depth of the third groove portion 232 of the second segment region 234 is 70 nm, the difference between the second filling factor of the second reflection region 236 and the second filling factor of the second segment region 234 closer to the branch region 220 than the second reflection region 236 is 0.1. On the other hand, when the difference between the depth of the third groove 232 of the second reflection region 236 and the depth of the third groove 232 of the second segmentation region 234 is 470 nm, the difference between the second filling factor of the second reflection region 236 and the second filling factor of the second segmentation region 234 closer to the branch region 220 than the second reflection region 236 is 0.00.

FIG7 (a) to FIG7 (d) are diagrams showing the brightness simulation results of an image formed on the pupil. The vertical axis and horizontal axis of FIG7 (a) to FIG7 (d) represent the positions of pixels. FIG7 (a) to FIG7 (d) show the results of simulating the brightness of the image under multiple conditions with different first fill factors in the first reflective area 226.

Conditions other than the first filling factor of the first reflection region 226 are described. The depth of the first groove portion 212 of the incident region 210 is greater than 100 nm and less than 200 nm. The length of the IPE period is greater than 350 nm and less than 450 nm.

The depth of the second groove 222 of the first segmented area 224a, the first segmented area 224b, and the first segmented area 224c is greater than 5 nm and less than 100 nm. The first period of the first segmented area 224a, the first segmented area 224b, and the first segmented area 224c is greater than 200 nm and less than 300 nm. The depth of the second groove 222 of the first reflective area 226 is greater than 100 nm and less than 700 nm. The first period of the second groove 222 of the first reflective area 226 is greater than 200 nm and less than 300 nm.

The depth of the third groove portion 232 of the second divided region 234 is greater than or equal to 5 nm and less than or equal to 100 nm. The first period of the third groove portion 232 of the second divided region 234 is greater than or equal to 350 nm and less than or equal to 450 nm.

The depth of the third groove portion 232 of the second reflection region 236 is greater than 100 nm and less than 700 nm. The first period of the third groove portion 232 of the second reflection region 236 is greater than 350 nm and less than 450 nm. The thickness of the glass substrate 112 is 0.4 mm. The length 248 from the first recess 222b to the glass substrate 112 is 100 nm.

FIG7 (a) is a simulation result when the first filling factor of the first reflection area 226 is 0.4. FIG7 (b) is a simulation result when the first filling factor of the first reflection area 226 is 0.5. FIG7 (c) is a simulation result when the first filling factor of the first reflection area 226 is 0.6. FIG7 (d) is a simulation result when the first filling factor of the first reflection area 226 is 0.85.

The dark areas in FIG. 7 (a) to FIG. 7 (d) indicate low brightness. As shown in FIG. 7 (a) to FIG. 7 (d), the further the first filling factor of the first reflection area 226 is from 0.5, the lower the unevenness of the brightness of the entire image and the more constant the brightness. In this way, by forming the second groove 222 and the third groove 232, the filling factor of the diffraction grating of the branch area 220 and the output area 230 becomes an appropriate value, which can reduce brightness deviation.

As described above, the projection substrate 100 of the present embodiment branches the projection light incident on the incident area 210 at different ratios corresponding to each of the plurality of first divided areas 224 of the branch area 220, and emits the projection light as image light from the emission area 230. Thus, the projection substrate 100 can reduce the unevenness of the brightness of the projection image viewed by the user. Furthermore, the projection substrate 100 also emits the image light at different ratios corresponding to each of the plurality of second divided areas 234 in the emission area 230, thereby further reducing the unevenness of the brightness of the image.

Such a projection substrate 100 can be realized by forming a diffraction grating corresponding to the incident area 210, the branch area 220, and the exit area 230 on the first surface or the second surface of a glass substrate. Furthermore, the groove portion forming the diffraction grating is, for example, an anti-etching agent, a resin, etc. Therefore, the projection substrate 100 of the present embodiment is a substrate as described below, that is, it does not need to be installed in a complex optical system, and can be simply produced by forming a groove portion with a predetermined period and depth in each area.

<Another example of the eyeglass type terminal 10> The example of the eyeglass type terminal 10 described below has been described, that is, the above-mentioned projection substrate 100 is set on the frame 110, and the projection unit 120 irradiates the projection light to the incident area 210 of the projection substrate 100, but it is not limited to this. For example, a plurality of projection substrates 100 may be fixed to the frame 110 of the eyeglass type terminal 10. Next, this eyeglass type terminal 10 is described.

FIG8 shows a modification of the spectacles type terminal 10 of the present embodiment. In the spectacles type terminal 10 of the modification, the same symbols are used for the operations that are substantially the same as those of the spectacles type terminal 10 of the present embodiment shown in FIG1, and the description thereof is omitted. The appearance of the spectacles type terminal 10 of the modification may be almost unchanged from that of the spectacles type terminal 10 shown in FIG1.

A plurality of projection substrates 100 are fixed to the frame 110 of the eyeglass type terminal 10 of the modification. At this time, the plurality of projection substrates 100 are fixed to the frame 110 in such a manner that the emission areas 230 provided on the plurality of projection substrates 100 at least partially overlap when viewed from above in a direction substantially parallel to the XY plane. FIG8 shows an example in which three projection substrates 100R, 100G, and 100B are fixed to the frame 110 of the eyeglass type terminal 10, and the emission areas 230R, 230G, and 230B of the three projection substrates 100 overlap when viewed from above on the XY plane.

The projection unit 120 irradiates projection lights of different wavelengths to the incident areas 210 respectively disposed on the plurality of projection substrates 100. Thus, the emission areas 230 respectively disposed on the plurality of projection substrates 100 emit image lights corresponding to the projection lights irradiated from the projection unit 120 to the plurality of incident areas 210 respectively from the second surfaces of the plurality of projection substrates 100 to the eyes of the user.

A user wearing such a glasses-type terminal 10 will see an image formed by overlapping image lights of different wavelengths, and thus can see an image with mixed colors. FIG8 shows an example in which the projection unit 120 irradiates three projection lights corresponding to the three primary colors of RGB, namely red, green and blue, which form an image, to the incident areas 210 of the three projection substrates 100, respectively. Furthermore, the three projection substrates 100 overlap the three image lights corresponding to the three primary colors of RGB and emit them to the user's eyes. Thus, the user can see images with ²ⁿ multiple colors, for example. Here, n is a positive integer such as 4, 8, 16, 24, etc.

The present invention has been described above using the embodiments, but the technical scope of the present invention is not limited to the scope described in the embodiments, and various modifications and changes can be made within the scope of its main purpose. For example, all or part of the device can be functionally or physically dispersed/integrated and constructed in any unit. Moreover, a new embodiment generated by any combination of multiple embodiments is also included in the embodiment of the present invention. The effect of the new embodiment generated by the combination has the effect of the original embodiment.

10: Eyeglass type terminal 20a: First input light 20b: Second input light 20c: Third input light 20d: Fourth input light 20e: Fifth input light 30a: First output light beam 30b: Second output light beam 30c: Third output light beam 30d: Fourth output light beam 30e: Fifth output light beam 100, 100a, 100b, 100B, 100G, 100R: Projection substrate 110: Frame 112: Glass substrate 120, 120a, 120b: Projection section 210: Incident region 212: First groove section 220: Branch region 222: Second groove section 222a: First convex section 222b: first concave portion 224a, 224b, 224c: first segmented area 226: first reflection area 230, 230B, 230G, 230R: emission area 232: third groove 234: second segmented area 236: second reflection area 240: line 242: space 244: spacing 246: depth 248: length C: circular area d: distance L, L1, L2: projection light M1, M2: image P: image light

FIG. 1 shows a structural example of the eyeglass type terminal 10 of the present embodiment. FIG. 2 shows a schematic diagram of the optical path of the projection light in the eyeglass type terminal 10 of the present embodiment. FIG. 3 shows a schematic diagram of the optical path of the projection light in the projection substrate 100 of the present embodiment. FIG. 4 shows an example of the projection light irradiated to the projection substrate 100 by the projection unit 120 of the present embodiment and the image light emitted by the projection substrate 100. FIG. 5 shows a structural example of the projection substrate 100 of the present embodiment. FIG. 6 is a diagram for explaining the first filling factor. FIG. 7 (a) to FIG. 7 (d) are diagrams showing the brightness simulation results of the image formed on the pupil. FIG. 8 shows a modified example of the eyeglass type terminal 10 of the present embodiment.

112: Glass substrate

220: Branch area

222: Second groove

222a: first convex part

222b: first recess

240: Line

242: Space

244: Spacing

246: Depth

248: Length

Claims (7)

A projection substrate is used to transmit at least a portion of light incident from a first surface to a second surface on the opposite side of the first surface, and to project image light onto the second surface, the projection substrate comprising: an incident area for incident projection light for projecting the image light; a branch area having a first diffraction grating for guiding the projection light incident from the incident area; and an exit area having a second diffraction grating for guiding a portion of the projection light incident from the branch area and then emitting a portion of the projection light from the second surface, the incident area The first diffraction grating has a plurality of first concave-convex portions formed by first convex portions and first concave portions, and the plurality of first concave-convex portions are formed in a manner of repeatedly guiding the projection light in a first direction, and the branch region has a plurality of first segmented regions, and a ratio of a width of the first convex portion in the first direction to a first period of the first concave-convex portion in one first segmented region, that is, a first filling factor, is not included. The first filling factor of the first segmented area closer to the incident area than the first segmented area is within a range including the specified value, the depth of the first concave-convex portion of the first segmented area is greater than the depth of the first concave-convex portion of the first segmented area closer to the incident area than the first segmented area, and the absolute value of the difference between the depth of the first concave-convex portion of the first segmented area and the depth of the first concave-convex portion of the first segmented area closer to the incident area than the first segmented area is The larger the value is, the smaller the absolute value of the difference between the first filling factor of the first segmented area and the first filling factor of the first segmented area closer to the incident area than the first segmented area is, wherein the specified value is 0.5, the first filling factor of the first segmented area farthest from the incident area among the multiple first segmented areas is within the range of 0.35 or less or 0.65 or more, and the first filling factor of the first segmented area closer to the incident area than the first segmented area is within the range of 0.3 or more and 0.7 or less. A projection substrate as described in claim 1, wherein the first period of the first concave-convex portion of each of the plurality of first divided regions is the same. A projection substrate is used to transmit at least a portion of light incident from a first surface to a second surface on the opposite side of the first surface, and to project image light onto the second surface. The projection substrate includes: an incident area for incident projection light for projecting the image light; a branch area having a first diffraction grating for guiding the projection light incident from the incident area; and an exit area having a second diffraction grating for guiding a portion of the projection light incident from the branch area and then emitting a portion of the projection light from the second surface. The incident area guides the incident projection light to the branch area, and the branch area guides a portion of the projection light. The first diffraction grating has a plurality of first concave-convex portions composed of a first convex portion and a first concave portion, and the plurality of first concave-convex portions are formed in a repetitive manner in a first direction for guiding the projection light. The branch region has a plurality of first segmented regions, and a ratio of a width of the first convex portion in the first direction to a first period of the first concave-convex portion in a first segmented region, i.e., a first filling factor, is within a range not including a specified value, and a first filling factor of a first segmented region closer to the incident region than the first segmented region is within a range including the specified value, and the first concave-convex portion of the first segmented region is within a range including the specified value. The depth of the first concave-convex portion of the first segmented area closer to the incident area than the first segmented area is greater, and the absolute value of the difference between the depth of the first concave-convex portion of the first segmented area and the depth of the first concave-convex portion of the first segmented area closer to the incident area than the first segmented area is greater, and the absolute value of the difference between the first filling factor of the first segmented area and the first filling factor of the first segmented area closer to the incident area than the first segmented area is smaller, wherein the second diffraction grating has a plurality of second concave-convex portions composed of second convex portions and second concave portions, and the plurality of second concave-convex portions are arranged in a manner that the first convex portion of the first segmented area is closer to the incident area than the first segmented area. The projection light is repeatedly formed in the second direction of the waveguide, the emission area has a plurality of second segmented areas, and the ratio of the width of the second convex portion in the second direction to the second period of the second concave-convex portion in the second segmented area closer to the branch area than the second segmented area among the plurality of second segmented areas, i.e., the second filling factor, is within the range including the specified value, wherein the specified value is 0.5, the second filling factor of the second segmented area is within the range not including the specified value, and the second filling factor of the second segmented area closer to the branch area than the second segmented area is within the range including the specified value. A projection substrate is used to transmit at least a portion of light incident from a first surface to a second surface on the opposite side of the first surface, and to project image light onto the second surface. The projection substrate includes: an incident area for incident projection light for projecting the image light; a branch area having a first diffraction grating for guiding the projection light incident from the incident area; and an exit area having a second diffraction grating for guiding a portion of the projection light incident from the branch area and then emitting a portion of the projection light from the second surface. The incident area guides the incident projection light to the branch area, and the branch area diverts a portion of the projection light toward the exit area. The first diffraction grating has a plurality of first concave-convex portions composed of a first convex portion and a first concave portion, and the plurality of first concave-convex portions are formed in a repeated manner in a first direction for guiding the projection light. The region has a plurality of first segmented regions, the ratio of the width of the first convex portion in the first direction to the first period of the first concave-convex portion in one of the first segmented regions, i.e., the first filling factor, is within a range that does not include a specified value, the first filling factor of the first segmented region closer to the incident region than the one of the first segmented regions is within a range that includes the specified value, the depth of the first concave-convex portion of the one of the first segmented regions is greater than the depth of the first concave-convex portion of the first segmented region closer to the incident region than the one of the first segmented regions, and the greater the absolute value of the difference between the depth of the first concave-convex portion of the one of the first segmented regions and the depth of the first concave-convex portion of the first segmented region closer to the incident region than the one of the first segmented regions, the greater the first filling factor of the one of the first segmented regions and the first filling factor of the first segmented region closer to the incident region than the one of the first segmented regions. The smaller the absolute value of the difference in factors, wherein the second diffraction grating has a plurality of second convex-concave portions consisting of second convex portions and second concave portions, and the plurality of second convex-concave portions are formed in a repetitive manner in a second direction for guiding the projection light, and the emission region has a plurality of second segmented regions, and the ratio of the width of the second convex portion in the second direction to the second period of the second convex portion in a second segmented region that is closer to the branch region than one of the second segmented regions, that is, the second filling factor is within the range including the specified value, wherein the specified value is 0.5, the first period of each of the plurality of first segmented regions is greater than 50nm and less than 1μm, the depth of the first convex-concave portion of the first segmented region is greater than 50nm and less than 800nm, and the first filling factor of the first segmented region is less than 0.35 or greater than 0.65 , the depth of the first concavoconvex portion of the first segmented area closer to the incident area than the first segmented area is greater than 5nm and less than 100nm, the first filling factor of the first segmented area closer to the incident area than the first segmented area is greater than 0.3 and less than 0.7, the second period of each of the plurality of second segmented areas is greater than 100nm and less than 1μm, the depth of the second concavoconvex portion of the second segmented area is greater than 50nm and less than 800nm, the second filling factor of the second segmented area is less than 0.35 or greater than 0.65, the depth of the second concavoconvex portion of the second segmented area closer to the branch area than the second segmented area is greater than 5nm and less than 100nm, and the second filling factor of the second segmented area closer to the branch area than the second segmented area is greater than 0.3 and less than 0.7. A projection substrate as described in claim 3 or claim 4, wherein the second period of the second concave-convex portion of each of the plurality of second divided regions is the same. The projection substrate as described in claim 3 or claim 4, wherein the depth of the second concavo-convex portion of the one second segmented area is greater than the depth of the second concavo-convex portion of the second segmented area closer to the branch area than the one second segmented area, and the greater the absolute value of the difference between the depth of the second concavo-convex portion of the one second segmented area and the depth of the second concavo-convex portion of the second segmented area closer to the branch area than the one second segmented area, the smaller the absolute value of the difference between the ratio of the width of the second convex portion in the one second segmented area in the second direction to the second period of the second concavo-convex portion, i.e., the second filling factor and the second filling factor of the second segmented area closer to the branch area than the one second segmented area. A glasses-type terminal for a user to wear, the glasses-type terminal comprising: the projection substrate as described in any one of claim 1, claim 3 or claim 4, provided as at least one of a lens for the right eye and a lens for the left eye of the user, allowing at least a portion of the light incident from the first surface to be transmitted to the eye of the user, and allowing the image light to be projected onto the second surface; a frame, fixing the projection substrate; and a projection unit, provided on the frame, irradiating the projection light for projecting the image light onto the emission area onto the incident area of the projection substrate.